1. Field of the Invention
The present invention relates to integrated circuits and, particularly, to a diode circuit that operates according to a voltage difference between two points in the circuit.
2. Description of Related Art
Devices using an integrated circuit have lower and lower voltage power supply. The trend toward a decrease in power supply voltage raises the need for a circuit to convert a voltage in a device. Known as a circuit used for part of the voltage conversion is a switching regulator as shown in FIG. 6. In this switching regulator, a control circuit 51 controls the pulse applied to a PMOS transistor P51. The output voltage is adjusted by the pulse control and by use of the characteristics of a schottky diode 52. In the switching regulator, the PMOS transistor P51 turns on if the voltage at an output node V52 is lower than a target voltage; it turns off if the voltage at the output node V52 is higher than a target voltage.
In the circuit of FIG. 6, the voltage at a node V51 can fall below a ground voltage Vss due to electromotive force of a coil in a smoothing circuit 53. In this case, a current flows from the ground voltage Vss to the node V51 through the schottky diode 52.
A technique described in Japanese Unexamined Patent Publication No. 2000-92824 uses a voltage comparator, a logic gate and a switch instead of the schottky diode of the circuit of FIG. 6.
A schottky diode is provided as an external component, which hinders miniaturization of an integrated circuit. The technique described in Japanese Unexamined Patent Publication No. 2000-92824 uses the voltage comparator and the logic gate so as to generate a signal according to a comparison result of the ground voltage and the voltage at the node V51. Since the switch operates according to this signal, this technique has a problem of a large circuit scale.